Custom fonts

It’s not entirely clear where you want to use the custom font: in the plugin’s UI or in the TextNode in the file?

If in the plugin’s UI, then you can include any font available at the URL using the <link> tag in HTML or @import/@font-face in CSS.

If in a TextNode, then only available fonts can be applied to it, which you can get via figma.listAvailableFontsAsync().